In a book completed in 1202, mathematician Leonardo of Pisa (Fibonacci) posed the problem: How many pairs of rabbits will be produced in a year, beginning with a single pair, if every month each pair bears a new pair that becomes productive from the second month on? The total number of pairs, month by month, forms the sequence 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, and so on. Each new term is the sum of the previous two terms. This set of numbers is now called the Fibonacci sequence... [and] the final digits repeat every 60 values. A cycle of 60 also plays an important role in the Chinese lunar calendar, and the coincidence of the Fibonacci cycle and the Chinese calendar cycle allowed
Seok Sagong of Middlesex Community College in Middletown, Conn., to establish a
one-to-one correspondence between the sequence of final digits of Fibonacci numbers and the names of years in the Chinese calendar.